The present invention relates to the field of electrical connectors, and, more particularly, to an electrical connector and associated manufacturing method.
Underground and submersible junction bus connectors are widely used in electrical power distribution systems. One type of such connector is offered under the designation SWEETHEART(copyright) by Homac Mfg. Company of Ormond Beach, Fla., the assignee of the present invention. The SWEETHEART(copyright) connector is a cast or welded aluminum connector including a bus, or bar, portion and a series of tubular posts extending outwardly from the bus portion. The posts have an open upper end to receive one or more electrical conductors. A threaded bore is provided in the sidewall of the post, and which receives a fastener to secure the electrical conductor within the upper end of the post. An insulating coating is provided on the lower portion of the posts and bus of the connector. In addition, EPDM insulating sleeves may be used to provide waterproof seals for the posts.
Unfortunately, the casting method for making such a connector may result in small trapped bubbles which leave internal voids in the casting. The internal voids may reduce the strength of the connector. The surface texture of the cast parts may be relatively rough, thereby requiring additional grinding or finishing steps. In addition, different molds are typically required for the different connector sizes and configurations. Accordingly, casting may be relatively expensive. In addition, a cast part may have a lower electrical conductivity.
U.S. Pat. Nos. 5,766,044; 5,555,620 and 5,608,965 each discloses an alternate approach to casting of the bus and post connector. A hollow-end milling cutter is used to form the entire extent of the upstanding posts from generally rectangular extruded stock material, and while also leaving the bus or bar portion at the base of the connector. In other words, an integrally formed monolithic connector is produced without casting and starting from extruded aluminum stock.
While the hollow-end milling approach offers a number of potential advantages, there are also shortcomings. In particular, a relatively large amount of the starting aluminum stock material must be removed and is therefore wasted. Also, the cost of the aluminum stock may also be relatively high because the stock must have a height dimension that is at least as great as the bus portion plus the full height of the posts. Of course, the number of required machining steps may increase the cost of the electrical connector produced by such hollow-milling cutter techniques.
In view of the foregoing background, it is therefore an object of the present invention to provide a method for making a bus and post connector without casting, and while reducing the waste and other drawbacks of the hollow-milling cutter approaches of the prior art.
These and other objects, features and advantages in accordance with the present invention are provided by a method comprising providing a bus and a plurality of posts, each post having a lower open end; positioning each post to have the lower open end adjacent a first surface of the bus; and displacing material from the bus into the lower open end of each post to secure each post to the bus. The bus and the posts preferably comprise an electrically conductive metal, such as aluminum. The method simplifies manufacturing of the connector, reduces waste compared to hollow-milling manufactured connectors, and may also overcome the disadvantages of a cast connector.
The displacing may comprise impacting at least the second surface of the bus. The displacing may also displace material from the bus radially outwardly to tightly engage adjacent portions of the post. Also, in some embodiments, each post may have a bore extending therethrough and the method may further include positioning a forming tool in the bore during the displacing or impacting.
In one class of embodiments of the invention, the displacing leaves the first and second surfaces of the bus continuous. In other words, a stub of bus material is displaced from the bus into the lower open end of the post and without punching through the bus. This forms a corresponding recess at the second or back surface of the bus.
In another class of embodiments, the method may further comprise forming respective openings in the bus for the posts. In these embodiments, the step of displacing comprises displacing edge material adjacent the openings into the lower open ends of the posts. The openings in the bus may permit the displaced material to extend further into lower open ends of the posts.
The bus may have a generally rectangular shape, such as in the shape of a bar. As mentioned briefly above, each post may be provided with a bore extending therethrough which defines the lower open end and also an open upper end for receiving at least one electrical conductor therein. Each post may also include at least one threaded passageway therein and extending transversely into the bore. The threaded passageway preferably receives a fastener to secure the electrical conductor in the post. Each post may also be provided with an increased thickness wall portion through which the threaded passageway extends to strengthen that portion of the post.
The connector may also include one or more different types of post. For example, the posts may comprise an uppermost tab with at least one opening therein for receiving a fastener to secure an electrical conductor thereto.
The method for making the connector may also include forming an insulating coating on at least the bus and lower portions of the posts. In addition, one or more posts may have different configurations, in terms or size and/or shape, than one or more other posts.
Another aspect of the invention relates to an electrical connector for connecting together a plurality of electrical conductors, as may be formed using the approaches described above. The connector preferably comprises a bus including a plurality of stubs extending outwardly from a first side and a corresponding plurality of recesses in the second side opposite the stubs, and a plurality of posts connected to the stubs. More particularly, each post has a lower open end engaged on a respective stub and an upper end to be connected to at least one electrical conductor. Since one method of making the connector uses displacement of material as described above, the volume defined by each recess may correspond to a volume of a corresponding stub.
In some embodiments, the first and second surfaces of the bus are continuous. In other embodiments, each stub has a bore extending therethrough, as these embodiments can be made by first forming openings aligned with the material that will be formed into the stubs.